Biomaterials 27 (2006) 1416–1424 In vitro hemocompatibility testing of UV-modified hyaluronan hydrogels Leena Pravina Amarnath, Arvind Srinivas, Anand Ramamurthi à Department of Bioengineering, Clemson University, Clemson, SC, Department of Cell Biology and Anatomy, Medical University of South Carolina, Charleston, SC 29425, USA Received 10 May 2005; accepted 11 August 2005 Available online 6 September 2005 Abstract Hydrogels (hylans) based on cross-linked hyaluronan (HA) are potentially good biomaterials for vascular tissue engineering applications because they are highly non-antigenic and -immunogenic. To facilitate surface endothelialization, vital to vascular deployment, we irradiated the gel surface with low wavelength UV light. This process micro-textures the smooth gel surface to provide sites for cell anchorage and causes limited scission of native long-chain HA yielding smaller fragments that elicit an enhanced cell response. In the current in vitro study, we assessed the effects of UV irradiation on the short-term (o45 min) interaction between hylan gels and human blood cells (RBCs, platelets) and coagulation proteins at physiologic temperature. Although the lowered hydrophilicity of irradiated (UV) hylans elicited greater vascular cell response relative to unmodified (U) hylans, platelet deposition was unaffected and much lower compared to collagen-coated glass controls. The adhered platelets were rounded or mildly pseudopodic and did not express p-selectin, an activation marker. Both gel types induced identical, and minimal platelet release as measured using an platelet factor 4 ELISA, and identically deferred the intrinsic and extrinsic coagulation pathways. Both gel types induced elevated levels of contact activation of bound, but not plasma-phase factor XII relative to controls. Hemolysis rates were also identical and within accepted standards. We conclude that UV-treatment of hylans, useful to improve surface endothelialization, does not compromise their short-term hemocompatibility, vital to their use as vascular implant materials. r 2005 Elsevier Ltd. All rights reserved. Keywords: Hylan; Ultraviolet; Blood-material interactions; Thrombosis 1. Introduction Currently, the long-term success balloon angioplasty techniques, used to re-vascularize blood vessels closed in by atherosclerotic plaques, is limited by rapid re-occlusion (restenosis) within 6 months of the procedure. Re-stenosis is particularly severe in small (o3 mm diameter) peripheral vessels which inherently tend to re-occlude much more severely than larger vessels [1] and respond unfavorably to the struts (stents) often deployed to prevent vessel collapse and re-closure [2]. Although multiple factors contribute to restenosis, a leading cause is the disruption of the protective lining of lumenal endothelial cells (ECs) during angioplasty, which exposes the highly thrombogenic sub- endothelial matrix and collagen to blood, whereupon platelets are recruited to the vessel wall. Upon contact with the injured tissue, platelets become activated, induce fibrin to crosslink, and form a platelet-fibrin thrombus. Thrombi are potent stimuli for neointimal thickening and hyperplasia of vascular smooth muscle cells. To address this problem, several previous studies [3–5] have attempted to isolate the injured tissue from blood using inert, synthetic barrier materials. However, these materials were not expected to endothelialize to provide longer-term protection against thrombosis, nor were they intended to signal the medial SMCs at the injury site to remain quiescent; also, such synthetic scaffolds are more likely to evoke non-physiologic cell responses and induce unnatural tissue healing. To address these issues, we are exploring the use of biocompatible, non-synthetic cell-scaffolds derived using components of tissue extracellular matrix ARTICLE IN PRESS www.elsevier.com/locate/biomaterials 0142-9612/$ - see front matter r 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.biomaterials.2005.08.008 à Corresponding author. Tel.: +1 843 792 5853; fax: +1 843 792 0664. E-mail address: aramamu@clemson.edu (A. Ramamurthi).